特殊环境服役的航空发动机高温防护涂层腐蚀行为与防护策略

Degradation Mechanisms and Protective Approaches for Aero-Engine Thermal Barrier Coatings Under Extreme Service Conditions

摘要:

随着航空发动机推重比的持续提升，热端部件服役温度接近2 000 K，这对高温防护涂层的耐极端环境腐蚀性能提出了严苛要求。在特殊环境（如盐碱地、海洋、沙尘环境）中，熔盐腐蚀、钙镁铝硅氧化物（CMAS）腐蚀等多因素耦合作用会导致涂层失效，成为制约航空发动机长寿命可靠运行的关键瓶颈。为此，系统地介绍了特殊环境下航空发动机高温防护涂层的腐蚀行为及防护策略的研究进展。对于熔盐腐蚀来说，主要的腐蚀介质是Na₂SO₄、NaCl和V₂O₅，这些熔盐首先侵蚀氧化钇部分稳定的氧化锆（YSZ）陶瓷面层，熔盐与YSZ中的Y元素反应，致使面层缺Y而发生由t相到m相的相变，随后熔盐渗透到热生长氧化物（TGO）层和粘结层NiCrAlY层，从而生成大量疏松多孔的氧化物。对于CMAS腐蚀来说，主要的腐蚀介质是CaO、MgO、Al₂O₃和SiO₂，由于CMAS腐蚀主要由沙尘等引起，因而会对航空发动机涡轮叶片产生机械作用和热腐蚀作用。机械作用是指沙尘高速冲击涡轮机叶片引发的冲蚀，以及熔融CMAS黏附在叶片上随飞机起降产生的循环热应力；热腐蚀作用是指熔融CMAS通过溶解-再沉淀机制，迫使ZrO₂因贫Y而发生的相变。这两种腐蚀类型的防护均可基于反应机理进行干预，通过阻断反应进程来实现防护效果，如覆盖一层保护层等。然而，根本的解决手段是对涂层材料进行优化与改进。当前，高温防护涂层针对环境问题的热点设计思路主要包括特色高性能防护温涂层的开发、YSZ涂层的改性及掺杂技术研究，以及高熵涂层的研发与应用探索。通过对特殊环境服役的发动机高温防护涂层腐蚀行为与防护策略的阐述，指出其未来发展的方向，为极端环境下高温防护涂层的研发提供了理论与技术参考。

Abstract:

With the continuous improvement of the thrust-to-weight ratio of aero-engines， the service temperature of hot-section components has approached 2 000 K， imposing stringent requirements on the extreme-environment corrosion resistance of high-temperature protective coatings. In special regions， such as saline-alkali lands， marine， and sand-dust environments， the coupling effects of multiple factors， including molten salt corrosion and calcium-magnesium-alumino-silicate （CMAS） corrosion， lead to coating failure， which has become a critical bottleneck restricting the long-life reliable operation of aero-engines. This paper systematically reviews the corrosion behaviors and protective research progress of high-temperature protective coatings for aero-engines in such extreme environments. For molten salt corrosion， the primary corrosive media are Na₂SO₄， NaCl， and V₂O₅. In thermal barrier coatings （TBCs）， these molten salts first attack the yttria-stabilized zirconia （YSZ） ceramic top layer. The molten salts react with yttrium （Y） in YSZ， causing Y depletion in the top layer and triggering a phase transformation from the tetragonal （t-phase） to monoclinic （m-phase）. Subsequently， the molten salts infiltrate the thermally grown oxide （TGO） layer and the NiCrAlY bond coat， generating large amounts of loose and porous oxides. CMAS corrosion is primarily caused by sand and dust， with corrosive components including CaO， MgO， Al₂O₃， and SiO₂. These components exert both mechanical and thermal corrosion effects on turbine blades. The mechanical effects involve erosion from high-speed sand-dust impacts and thermal stress induced by the adhesion of molten CMAS during engine operation cycles （e.g.， takeoff and landing）. The thermal corrosion effects refer to the dissolution-reprecipitation mechanism of molten CMAS， which forces ZrO₂ to undergo phase transformation due to Y depletion. Protection strategies against both corrosion types can start from interrupting the reaction mechanisms， such as applying a protective layer. However， a more fundamental approach involves modifying the coating itself. Current research hotspots in high-temperature protective coatings for environmental challenges include specialized high-temperature coatings， improved and doped YSZ coatings， and high-entropy coatings. Finally， this paper summarizes the progress in high-temperature protective coatings for engines operating in special regions and proposes future development directions.